The color of used oil tells us....

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I have read where people say their motor oil comes out almost the same color as it went in.

Any vehicle I have owned that I changed the oil came out dark brown to black.

Is it just the oil make up or are some vehicles just super easy on oil and clean inside?
 
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It tells me that for the people that have the same color coming out as going in they are wasting their time and money. They are changing way earlier than necessary.
 
Originally Posted By: CPB
It tells me that for the people that have the same color coming out as going in they are wasting their time and money. They are changing way earlier than necessary.


Either this or they didnt remember the color it was when going in. A small difference in color is common with some cars. I notice mine does get darker but not super dark. Golden going in, dark golden/light brown coming out.
 
Originally Posted By: newbe46
I have seen the oil turns into almost a grey-ish colour. Thanks god it wasn't one of my own vehicles.

Why? What does that indicate?
 
Originally Posted By: kschachn
Originally Posted By: newbe46
I have seen the oil turns into almost a grey-ish colour. Thanks god it wasn't one of my own vehicles.

Why? What does that indicate?


Possible coolant in the oil. One of the very few times a UOA is really needed.
 
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Originally Posted By: tig1
Originally Posted By: kschachn
Originally Posted By: newbe46
I have seen the oil turns into almost a grey-ish colour. Thanks god it wasn't one of my own vehicles.

Why? What does that indicate?


Possible coolant in the oil. One of the very few times a UOA is really needed.


This happened when I helped a buddy to change the oil in his Mazda 5. He claimed he overran that OCI but didn't know for how much. He doesn't care much about anything let alone a UOA so I didn't even bother bringing it up.
 
I remember somebody online (here?) telling a story about the owner of a used car lot putting non-detergent oil in all of his vehicles up for sale so it would look as good as out of the bottle if a customer happened to pull the dipstick. Not sure how realistic that is, but it's a good story.

My oil comes out quite dark after 5kmiles, my assumption is that it's due to the heat of the turbo. I used to darken it myself with a MoS2 additive, but I don't do that anymore.
 
Oil change color because it does what it is supposed to do which is lubricating.

The oil in diesel engine goes black because it suspends the soot.
 
Originally Posted By: ZZman
The color of used oil tells us....


Next to nothing - at least not reliably, and between platforms. For one vehicle using the same oil, maybe.
 
My old '81 F250 straight 6 on propane got a yearly oil change regardless of miles and the oil was light amber. Never used any special oil, just what was the cheapest. Still that way after 350K miles and new owner. He can't believe it.
 
The color? Nothing.

Only if there are sparkles in there, chunks, foam, or it's milky, you have a visual indication of a problem. Really.
 
I think fuel quality may also have an impact on this. When I managed a warehouse, I was responsible for making sure the fork lift was maintained. It ran on LP, and couldn't help but notice that even at the service interval hours, the oil was still very clear and gold colored. There was literally no way to tell if the oil had actually been changed unless they spilled some (which they did). I guess LP leaves no combustion deposits, so if you go by color, you'd never change the oil. Maybe some fuels are 'cleaner' than others and it's reflected in the oil color.
 
Originally Posted By: pkunk
My old '81 F250 straight 6 on propane got a yearly oil change regardless of miles and the oil was light amber. Never used any special oil, just what was the cheapest. Still that way after 350K miles and new owner. He can't believe it.


Gaseous fuel burns without soot (Propane is stored as a liquid, but you have a heated regulator and a diaphragm-type carburetor to turn it into a gas), so you won't get darkening of the oil the same way you would from liquid fuels.

My instructor for the LPG vehicle course harped on the fact that oil won't get dark and needs to be changed as the additives wear out, that spark plugs tend to need to be one or two steps cooler to last, run better, and get better power, and that based on tailpipe tests a badly tuned propane engine pollutes much more than a gas engine. A well tuned one pollutes a whole lot less. Oh, and to run a much cooler thermostat, since propane engines care less about engine temperature, nor do their emissions because of it.

And yes, with proper maintenance, they run a really long time. You're not burning a solvent that dilutes the oil coat on your cylinder walls, for starters. And engines specifically built for the fuel can be super awesome, I remember being able to lay a strip in a 3-ton 30' panel van with a 4-on-the-floor and dualies pretty much at will. I'd run that fuel today if I could.
 
ZZman, how long are your change intervals?

While I would not say my oil comes out the same color it went in, it is only a little darker.
Here is my dipstck with just over 3000 miles/8 months on the oil (38,000 miles on the car).
full-4879-10061-1.jpg


Here is a coffee filter with a few oil blots, 3 of the "old" oil, and 1 of new oil (circled in red).
full-4879-10062-2.jpg


same blot a week later
full-4879-10176-3_days.jpg


So it is a dark honey color after 3000 miles.

Also, on my sisters Hyundai, I noticed that even after 10,000 miles the oil was not very dark when draining it. Again, darker than new, but no way real dark.

My truck is very dark when I drain it.


Rolla07 has a good point, maybe they don't remember what it looked like going in.
 
Originally Posted By: blupupher
ZZman, how long are your change intervals?

While I would not say my oil comes out the same color it went in, it is only a little darker.


Usually around 5-6,000
 
Originally Posted By: zuluplus30
Tells me nothing. All speculation until a lab confirms it.


+1
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Unless there is an obvious sign of trouble like fuel in the oil where it can be smelled or the oil is creamy brown or grey which indicates a possible coolant leak.
 
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Originally Posted By: zuluplus30
Tells me nothing. All speculation until a lab confirms it.

What properties would the lab confirm that are inferred from a blotter test?
 
Originally Posted By: kschachn
Originally Posted By: zuluplus30
Tells me nothing. All speculation until a lab confirms it.

What properties would the lab confirm that are inferred from a blotter test?


About the same properties they could get off your used TP.
 
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